There is increasing evidence for relict or currently active glaciers in Tharsis on Mars:

exoscientist
12/07/02 05:22 PM
Current glaciers in Tharsis, Mars?
http://uplink.space.com/showthreaded.php?Cat=&Board=sciastro&Number=371198

Part of the reason for saying this are geologically recent liquid water cut channels in Tharsis:

Title: Recent Water Release in the Tharsis Region of Mars
Authors: Mouginis-Mark, P. J.
Journal: Abstracts of the Lunar and Planetary Science
Conference, volume 20, page 727, (1989)
"The fluvial channels identified here demonstrate that melt water release took place in isolated areas within northwestern Tharsis over a very extended period of martian history, and includes episodes that post-date the emplacement of some of the youngest lava flows on the planet. While the origin and physical setting of the water remains unclear, these observations lend additional support to three popular views of the volatile history of Mars: 1) that ice lenses may have been preserved for extended periods at shallow depth over much of Mars, including the near-equatorial latitudes; 2) that _in certain very specific localities_ Mars may have been a wet planet until geologically recent times; and 3) that local igneous activity most likely served as a catalyst for melt water release at the surface."
http://adsabs.harvard.edu/cgi-bin/bib_query?1989LPI....20..727M

Title: Recent water release in the Tharsis region of Mars
Authors: Mouginis-Mark, P. J.
Journal: Icarus (ISSN 0019-1035), vol. 84, April 1990, p. 362-373. http://adsabs.harvard.edu/cgi-bin/bib_query?1990Icar...84..362M

This was based on Viking imaging.
I found an MGS image that I thought might indicate quite recent, perhaps currently forming, liquid water cut channels in Tharsis:

Sample Tharsis plain
http://ida.wr.usgs.gov/html/e02005/e0200557.html

There are some craters in the image. But the larger ones are frequently cut by the channels, which suggests the channels postdate the larger craters.
The shallowness of the channels would also seem to suggest relative youth based on the resolution of the image. The dendritic (like a tree branching) and anastomosing (channels that break off from the main channel and rejoin to it) features suggest the channels were carved by flowing water. See image below.

If there is near surface ice in this region, since the area
was volcanically active and likely continues to be, some of
these craters may actually be maars or tuff rings, which are formed from volcanic/water interaction not meteorite impact.
This recent THEMIS release also shows apparently recent channels in Tharsis:

Unusual Crater (Released 15 May 2003)
http://themis.la.asu.edu/zoom-20030515a.html

I found after searching on the THEMIS site some images from in approximately the same area as the channels Mouginis-Mark observed that also suggest apparent youth:

Ulysses Fossae
http://themis-data.asu.edu/img/V01627006.html

Ulysses Fossae
http://themis-data.asu.edu/img/V01964009.html

Ulysses Fossae
http://themis-data.asu.edu/img/I01964008.html

Ulysses Fossae
http://themis-data.asu.edu/img/I01627005.html

Ulysses Fossae
http://themis-data.asu.edu/img/I01889005.html

Systematic Mapping - 27 to 9N
http://themis-data.asu.edu/img/I02051002.html

systematic mapping
http://themis-data.asu.edu/img/I02126005.html

Systematic Mapping
http://themis-data.asu.edu/img/I02201005.html

Systematic mapping
http://themis-data.asu.edu/img/I02363007.html

Tharsis flatfield region
http://themis-data.asu.edu/img/I01664006.html

Tharsis flatfield calibration
http://themis-data.asu.edu/img/I02413005.html

If the channels are currently forming it may be possible to detect new channels from the THEMIS images of this region compared to the prior MGS images.
The descriptions accompanying some of the THEMIS images refer to the channels as fossae, which suggests they are due to tectonic activity. However referring to the MGS image E0200557, it is clear some of these channels cut into craters in the form of liquid water flow. So undoubtedly at least some of the "fossae" in the THEMIS images are also due to liquid water flow.
Note also that McKenzie and Nimmo have written that the linear faults seen on Mars could be due to dikes that could generate floods by melt of overlying ice:

The generation of martian floods by the melting of ground ice above dykes.
Dan McKenzie & Francis Nimmo
"The surface of Mars is cut by long linear faults with displacements of metres to kilometres, most of which are thought to have been formed by extension. The surface has also been modified by enormous floods, probably of water, which often flowed out of valleys formed by the largest of these faults. By analogy with structures on Earth, we propose here that the faults are in fact the surface expression of dykes, and not large-scale tectonic movements. We use a numerical model to show that the intrusion of large dykes can generate structures like Valles Marineris. Such dykes can provide a heat source to melt ground ice, and so provide a source of water for the floods that have been inferred to originate in some of the large valleys."
NATURE, VOL 397, 21 JANUARY 1999
http://bullard.esc.cam.ac.uk/~nimmo/paper9.pdf

This would be especially relevant to Tharsis if there is glacial ice still extant there.

Bob Clark

Image in Tharsis showing dendritic channels.